1. Field of the Invention
This invention relates to a low-noise battery power supply apparatus suited to low-noise measurement systems or to the measurement of characteristics of electronic circuits such as ultra high-sensitivity sensor elements wherein AC power noise from the outside has a large effect on the operating characteristics and results of measurement.
2. Description of the Prior Art
Variable AC/DC voltage power supplies that rectify AC power to generate DC always contain roughly 0.1 microvolt of power supply noise, so they cannot be used as the variable AC/DC voltage power supplies for low-noise measurement systems or electronic circuits such as ultra high-sensitivity sensor elements (ultra-sensitive light or microwave sensors, or SQUID, SIS/SNS or other Josephson effect devices, etc.) wherein AC power noise from the outside has a large effect on the operating characteristics and results of measurement. To this end, batteries are conventionally used in the case of performing measurements on materials when AC power noise has a large effect on the operating characteristics and results of measurement in this manner, so in order to obtain the required current or voltage, it is necessary to connect batteries in series or vary the value of the resistance connected in series with the batteries, thereby obtaining a power supply suited to the purpose.
FIG. 9 shows the aforementioned conventional battery-powered circuit for applying current/voltage to a specimen. This battery power supply is enclosed within a shield case that shields out noise induced from outside, and at the time that the current or voltage applied to the sample 5 is adjusted, the variable resistor 2 or number of batteries 1 must be manually changed each time to construct a circuit, and moreover, an ammeter 3 or voltmeter 4 must be used to confirm manually the required current or voltage. In addition, the individual batteries are manually isolated and measured, and then recharged or replaced with new batteries to confirm the battery voltage that drops with use of the battery.
In this manner, when a conventional battery power supply is used as a low-noise- power supply, every time it is necessary to change the current or voltage, it is necessary to separate the battery power supply circuit from the measurement system and manually adjust it, making the work extremely complicated.
On the other hand, in the event that a simple function for automatically adjusting the current/voltage of the battery power supply (a function for automatically switching batteries or resistance values) is added, noise arising from the power supply circuits and the like for operating this automatic adjustment function become an obstacle, giving rise to the possibility of having large effects on the sample operating characteristics/measurement results. In addition, since the power supply circuit itself is enclosed within a shield case, it is necessary to provide functions for command and control or information collection with respect to the automatic adjustment function outside of the shield case, so control signal lines must be extended from the shield case, and there is a possibility that noise introduced via these signal lines will have a large effect on the sample operating characteristics/measurement results.
The present invention was proposed in light of the above. Its object is to provide a battery power supply apparatus wherein the adjustment and control of the current/voltage to the outside can be performed efficiently and also the introduction of noise at the time of supplying power to the outside can be suppressed as much as possible.
To attain the above object, the battery power supply apparatus according to the present invention comprises: power supply means, enclosed within a shield case that shields out noise induced from outside, that is able to make fine adjustments to the current/voltage output to the outside by means of a combination of a plurality of batteries and variable setting of resistance values, command and control means that performs command and control of said power supply means, and bidirectional transmission means that, by converting electrical signals sent out from said command and control means into optical signals or acoustic signals and transmitting same to the power supply means and also converting optical signals or acoustic signals sent out from the power supply means into electrical signals and transmitting same to the command and control means, is able to induce an electrically insulated state between the power supply means and command and control means and also suppress the introduction of noise into the power supply means within the shield case; wherein said power supply means comprises: startup/shutdown control means that receives the power required for operation from a battery, and upon receiving an optical signal based on a startup command from said command and control means, enables the supply of operating power to various functional blocks within the power supply means, and upon receiving a shutdown command from the command and control means, shuts off the supply of operating power to various functional blocks within the power supply means, battery control means whereby the number of a plurality of batteries connected in series can be selectively set, and the selectively set state can be maintained even after the operating power is shut off, resistance control means whereby the resistance connected to the power supply circuit consisting of batteries selected by the aforementioned battery control means can be variably set arbitrarily, and the variably set state can be maintained even after the operating power is shut off, power supply control means that, based on power supply control commands from said command and control means, performs the selective setting of batteries by said battery control means and the variable setting of the resistance value by said resistance control means, and thus controls the current/voltage supplied from the battery-based power supply circuit, wherein, after the current/voltage supplied to the outside from the power supply circuit of the power supply means is adjusted, it is possible to shut off the supply of operating power by the startup/shutdown control means and eliminate noise generated from the various functional blocks within the power supply means, thereby providing a low-noise battery power supply.
In addition, the aforementioned battery power supply apparatus comprises: a battery-based constant-current power supply, a battery control means and a switching means that is able to switch either a power supply circuit set by a resistance control means or a power supply circuit based on the aforementioned constant-current power supply to be the power supply circuit to the outside, wherein a minute current from the constant-current power supply is applied to both ends of a sample connected to the battery power supply apparatus, and the voltage between said both ends is measured to measure the resistance of the sample.
In addition, the aforementioned battery power supply apparatus is one wherein said switching means has a function for switching between connecting and disconnecting a measuring instrument that measures the current/voltage applied to the sample.
In addition, the aforementioned battery power supply apparatus comprises charging means for charging batteries within the power supply means that is automatically started upon receiving a supply of power from outside.
As described above, by means of the battery power supply apparatus according to the present invention, the power supply means that supplies power to the outside and the command and control means that performs command and control of said power supply means perform bidirectional communications by means of the bidirectional transmission means, and thus it is possible to prevent noise arising in the command and control means from reaching the power supply means and also, it is possible also to prevent the introduction of noise from the signal transmission path into the power supply means within the shield case. Accordingly, it is possible to perform control of the operation of the power supply means enclosed within the shield case from the command and control means outside of the shield case without having external noise affecting the power supply means. Moreover, based on commands from the command and control means, the power supply control means performs control of the battery control means and resistance control means, thus adjusting the current/voltage supplied to the outside from the power supply circuit of the power supply means and then, the startup/shutdown control means shuts off the supply of operating power, thereby eliminating noise generated by various functional blocks within the power supply means. Furthermore, the set states of the battery control means and resistance control means are maintained even after the operating power is shut off, so it is possible to continue the supply of battery power to the outside at the desired current/voltage settings at low noise.
Accordingly, the battery power supply apparatus according to the present invention can efficiently perform the control of adjustment of the current/voltage supplied to the outside and also, the introduction of noise at the time of power supply to the outside can be suppressed as much as possible, thus becoming a low-noise battery power supply apparatus suited to low-noise measurement systems or the measurement of characteristics of electronic circuits such as ultra high-sensitivity sensor elements wherein AC power noise from the outside has a large effect on the operating characteristics and results of measurement.